I bought a car that has quite a sound system in it and it also has a capacitor for it. When I originally bought it, I was shown I needed to to turn off the capacitor every time I turned the car off or else the battery would drain and it wouldn't start. After having the car for a bit, I had a lot of work done and the stereo was never hooked back up. Over the time I drove the car without the stereo hooked up, the car started perfect every time.

Just recently I had the stereo hooked back up without the capacitor being wired in and now the battery is being drained so when I let it sit overnight, the battery is too low to turn over the engine. The electric shop is telling me that the " di charge" isn't strong enough, even though it's a seriously heavy duty alternator.

I took the car back to the shop and had them hook up the capacitor along with the on off switch. When I started the car at the shop, the capacitor read 13.5 and when I reached home after playing the stereo on the drive home, the capacitor read 11.9.

So my question is, is the wiring faulty somewhere, is the alternator not generating enough juice, or is there some other suspected problem?

is there a solution where I can get rid of the capacitor yet have the battery always having a full charge?

Do you have a VOA multimeter and the knowledge to use it ? Simply, the alternator charges the battery, the battery powers the loads. A capacitor - in a stereo installation - handles the sudden need for more power caused by a loud passage in music. They work as a battery with a quick response time. Your post above said the capacitor shows 13.5 volts at startup, but 11.5 volts when you arrive home. Is this capacitor connected directly to the battery ? You will need to use the VOA meter to determine if the alternator is putting out enough to keep the battery charged during your drive. If it is - the battery itself may be bad.

It’s not the volts that matter, it’s the Amperes taken out overnight. Here’s a simple check. Disconnect the plus cable at your battery and switch an Ampere meter between the + pole at battery and the other wire of your meter at the plus cable.

As we already know that it’s your stereo that empties your battery, it’s much easier to troubleshoot. The direct + is called 30, while the power that comes when you switch your ignition on has the number 15. (Just in case you’ll reconnect your system)

I think that somebody connected your stereo the wrong way, Thais aren’t good in electric/ electronical things, the wrong wires, so the 30 – direct plus and 15- through the ignition lock are wrongly connected. Have you got a receiver?

Please check your wiring system if I’m right. Then you only have to connect the # 30 cable direct to the battery (which is usually one with a fuse, if not put one in) and the other one with the # 15 which brings power from your ignition lock.

Please see: http://www.popularmechanics.com/cars/how-to/a5859/how-to-stop-car-battery-drains/

Do you have a VOA multimeter and the knowledge to use it ? Simply, the alternator charges the battery, the battery powers the loads. A capacitor - in a stereo installation - handles the sudden need for more power caused by a loud passage in music. They work as a battery with a quick response time. Your post above said the capacitor shows 13.5 volts at startup, but 11.5 volts when you arrive home. Is this capacitor connected directly to the battery ? You will need to use the VOA meter to determine if the alternator is putting out enough to keep the battery charged during your drive. If it is - the battery itself may be bad.

But then he would have the problem to get his car started, if that's true.

P.S,. Sorry. after reading the OP and your post again, it could also be a faulty battery. One cell that's going to die, as it should never be under 12 volts.

Are the amps turning off when you turn off the ignition, if they are not then they are hard wired and that will be the cause, they need to be switched (usually by the stereo head unit which will be a single blue wire).

If you are dropping to 11.5 volts it sounds to me like a dead battery or failing alternator.

If you decide to remove the cap remember to drain it.

Are the amps turning off when you turn off the ignition, if they are not then they are hard wired and that will be the cause, they need to be switched (usually by the stereo head unit which will be a single blue wire).

If you are dropping to 11.5 volts it sounds to me like a dead battery or failing alternator.

If you decide to remove the cap remember to drain it.

Checking your alternator is relatively easy. All you need is a voltmeter, connect the red wire to plus and the black wire to minus at your battery.

Start your car, switch all on, including lights and read your voltage.

If the alternator is charging well, you'll read around 13.8 volts. If you switch all off, including the engine,and the battery voltage drops below 12 volts, your battery is gone to heaven.

Unfortunately I don't have any electrical testing equipment. This afternoon I warmed up the car at a fast idle and before I left, the capacitor registered 12.4. I then drove about 10 minutes before shutting the car down for two hours. I then came home driving the same 10 minutes and I checked the reading before shutting it down, and it read 12.8. I didn't turn on the stereo at all and kept the capacitor turned off (which connects directly to the battery).